Room 304, Chemistry Building
Professor Younan Xia
Georgia Institute of Technology
Although the first documented synthesis of colloidal metal nanocrystals can be traced back to the beautiful work on gold colloids by Michael Faraday in 1856, only within the last decade have methods become available for generating samples with the quality, quantity, and reproducibility needed for a systematic study of their properties as a function of size, shape, and structure, and for exploration of their applications. Of particular importance is to control the shape of colloidal metal nanocrystals, which may initially seem like a scientific curiosity but with implications going far beyond aesthetic appeal. For nanocrystals made of noble metals, the shape determines not only their chemical, plasmonic, and catalytic properties but also their relevance for electronic, photonic and catalytic applications. For more than 15 years, we have been working diligently to achieve a quantitative understanding and control of the nucleation and growth mechanisms responsible for the formation of nanocrystals with specific shapes and structures. We have discovered that the shape of metal nanocrystals are dictated by surface capping and the crystallinity and structure of seeds, which are, in turn, determined by factors such as reduction kinetics and oxidative etching. In this talk, I will discuss some of the recent developments in this field, with a focus on shape-controlled synthesis of noble-metal nanocrystals via seed-mediated growth in the presence/absence of a capping agent and under a thermodynamic or kinetic control. The success of these syntheses has enabled us to tailor the properties of metal nanocrystals for a broad range of applications in photonics, sensing, imaging, biomedicine, catalysis, and fuel cell technology.